Add support for phpstan/phpstan:2.0.0

I've created a MR so we can see if the tests are still green.

I've updated the MR to also allow phpstan/phpstan-deprecation-rules version 2 because otherwise, we would still get PhpStan version 1.

I've tested the MR locally and it now works by pulling the latest PhpStan version and also the latest mglaman/phpstan-drupal

Leaving the status at NR as I've changed the MR, so I can't move it to RTBC.